1. Field of the Invention
The field of the invention is inhalers for dry powder inhalants or drugs.
2. Description of the Prior Art
Certain medicines may be administered in dry-powder form directly to the lungs by inhalation through the mouth or inspiration through the nose. This process allows the medicine to bypass the digestive system, and in some cases, allows smaller doses to be used to achieve the same desired results as orally ingested medicines. In other cases, it provides a delivery technique for medicines that display unacceptable side effects when taken by other methods.
Various devices or nebulizers that form inhalable mists of medicines have been known and used. These devices form mists of liquid medicines, powdered medicines, or from both liquids and powders. However, these known devices have various disadvantages, including lack of efficiency in delivering the medicine or drug; difficulties in loading and use requiring substantial manual dexterity; the need for repeated deep inhalation; non uniform dosing; caking of powdered medicines; and others.
Another important factor is that it has not been realized that several important benefits are obtained if the delivery of a drug is relatively independent of the patient's inspiratory flow rate (i.e., how deeply the patent inhales) or coordination (i.e., the patient's timing of the inhalation). An inspiratory flow rate independent device can be used by patients with low inspiratory flow rates, such as children or patients experiencing aspiratory distress. Moreover, if the delivery of a drug is independent of the patient's inspiratory flow rate, the inhaled dosage will remain relatively consistent regardless of the patient's inhalation characteristics. Metered dose inhalers, typically using a propellant gas, require significant coordination for proper use. Actuation must occur during inspiration, or the majority of the drug will be deposited in the throat. It is now appreciated that a breath-actuated device will minimize the need for patient coordination.
Moreover, the beneficial effects of reducing the size of large particles or agglomerated particles during use of inhalation devices have apparently not been appreciated previously. Large or agglomerated particles of medicine gather momentum during forced inhalation or inspiration and impact the soft, wet tissue surrounding the throat and larynx instead of remaining in the air flow for deposit in the lungs. When this occurs, much of the medicine apparently does not reach deep into the interior of the lungs and thus is not placed in a strategic location where it will be solvated for direct absorption through the areolar tissue into the blood stream. In more severe cases, such impact may cause coughing and thus could force large volumes of moisture-laden air, as well as finely dispersed saliva, to be reinjected into the device leading to caking of the medicine.
Accordingly, it is an object of the invention to provide an improved dry powder inhaler.